Triple-layer perpendicular recording media for high SN ratio and signal stability

Media noise, SN ratio, and signal stability of triple-layer (TL) perpendicular recording media are studied. The TL medium is composed of a CoCrTa perpendicular layer, an amorphous CoZrNb soft magnetic layer, and a CoSm in-plane hard magnetic pinning layer. A high SN ratio is obtained due to the pinning effect of the CoSm layer and with an optimum CoCrTa perpendicular layer of a 50-nm-thick Co-Cr20-Ta3.5at% (Ms=400 emu/cm/sup 3/) film. High signal stability against stray magnetic fields is obtained in TL media with a 600-nm-thick CoZrNb layer. Moreover, no thermal magnetic relaxations occurs in TL media at 60/spl deg/C for 5 hours and at room temperature for 15 hours. The TL media are promising as practical ultrahigh-density recording media having high read-write reliability.